Nymphs and Emergers
Fish Eat Nymphs and Emergers because they are a Plentiful Food Source
Nymphs are immature insects that live underwater and are an important food source for many species of fish, including trout and other gamefish. Emergers are insects that are transitioning from the nymph to the adult stage and imitate insects such as midges, mayflies, and caddis. They are particularly vulnerable to predatory fish at this stage.
In general, nymphs are most active and available as a food source during the spring and fall, when many insects are hatching. Emergers are usually most abundant during the warmer months when insects are emerging from their nymphal stage.
Nymph flies are best fished along the bottom and emergers in the middle to the upper part of the water column.
Whenever possible, try to match the hatch by selecting flies that imitate the lifecycle and behavior of insects in your area. Understanding the feeding habits of local fish and what they are feeding on will help you catch more fish.